Carburetor control mechanism

ABSTRACT

In a carburetor including a choke valve and a throttle valve, a control mechanism is provided which comprises linking means interconnecting the choke valve and the throttle valve in a manner whereby movement of the choke valve from its open position to its closed position causes the throttle valve to move at a continuously decreasing rate of motion toward its open position.

United States Patent [191 Kobayashi et al.

[ Sept. 23, 1975 CARBURETOR CONTROL MECHANISM [75] Inventors: NobuyukiKobayashi; Mitsunori Sasano; Masahiko Nakada, all of Toyota, .lapan [73]Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha, Japan 22 Fi1ed: Julyll,1974 211 App1.No.: 487,736

[30] Foreign Application Priority Data Nov. 30, 1973 Japan 48-133565[52] US. Cl. 261/52; 261/39 A; 261/43; 251/233; 137/614.l1; 123/119 F[51] Int. Cl. F16k 11/22 [58] Field of Search 137/614.l l; 261/52, 43,261/182R, 39 A; 123/119 F;

[56] References Cited UNITED STATES PATENTS 1,456,502 5/1923 Hartwell261/52 2,156,390 5/1939 Henning l23/l 19 F 2,448,043 8/1948 Nash3,807,709 4/1974 Suda et al. 26l/39 A Primary Examiner-William R. ClineAttorney, Agent, or Firm-Tore'n, McGeady and Stanger [57] ABSTRACT In acarburetor including a choke valve and a throttle valve, a controlmechanism is provided which comprises linking means interconnecting thechoke valve and the throttle valve in a manner whereby movement of thechoke valve from its open position to its closed position causes thethrottle valve to move at a continuously decreasing rate of motiontoward its open position.

8 Claims, 3 Drawing Figures US Patent Sept; 23,1975

62 0| FULLY CHOKE OPENING CLOSED I z z I r z I E W PNO m mm W TE.lllilii Gu AR @255 U mm MT fltomfi E mm M M IIE NE GT GT W NL 0 EA mmcm mm fULLY @PENED CARBURETOR CONTROL MECHANISM BACKGROUND OF THEINVENTION The present invention relates generally to a control mechanismfor a carburetor used in vehicles such as automobiles, and moreparticularly to a choke control device whereby a choke valve is linkedwith a throttle valve of the carburetor for interdependent movementtherebetween. The mechanism of the present invention is particularlysuited for use with manual choking de' vices.

Conventional automobiles do not exhibit optimum performancecharacteristics during the warming-up phase of their operation. Suchengines are designed so that at the time of cold engine idling at normalor low temperatures the choke valve of the engine carburetor ismaintained near its closed position to provide a richer fuel and airmixture. Consequently, under such conditions, a relatively largequantity of unburned detrimental CO or I-IC components will be containedin the engine exhaust gases. Such circumstances are undesirable in viewof the fact that they aggravate the problem of air pollution caused byautomotive exhaust gases. In order to overcome such problems, effortsare being made to develop engines which exhibit superior warming-upperformance wherein engine idling under the conditions described abovemay be effected with a lean fuel mixture. In such engines it becomesunnecessary to move the choke valve to a substantially closed conditionand the engine is able to operate satisfactorily during warm-up withoutincreasing the deleterious components in the exhaust gases.

Thus, it becomes advantageous to provide a choke mechanism whereby thecold engine idling at normal temperatures may be effected without thechoke valve being brought to its fully closed condition and with thethrottle valve being maintained at an appropriate opening for engineoperation, since under such idling conditions the amounts of unburned,detrimental components contained in the exhaust gases may be greatly reduced.

In view of theforegoing, the present invention aims at providing amanually operated choke device which is applicable in an engineexhibiting good warm-up performance, and in which the choke valve may belinked with the throttle valve so that it may be operated in aninterrelated manner. By application of the present invention, there maybe provided a choke device which can greatly reduce the amounts ofunburned, detrimental components contained in exhaust gases during thetime of cold engine idling.

SUMMARY OF THE INVENTION Briefly, the present invention may be describedas a control mechanism for a carburetor including a choke valve and athrottle valve each operable to be moved between a closed position andan open position, said control mechanism comprising linkage meansinterconnecting said throttle valve and said choke valve forinterdependent movement thereof, said linkage means being configured tocause the position of the throttle valve to be moved at a relativelylower rate when the choke valve is moved in the region near its closedposition, and at a relatively higher rate when the choke valve is movedin the region near its open position.

The choke and throttle valves are interconnected so that as the chokevalve is moved from its open position to its closed position, itsinitial effect upon the throttle valve is to move it toward its openposition at a higher rate with the'rate of movement of the throttlevalve toward the open position decreasing as the choke valve is broughtto its closed position. 1

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects atained by its use,

. reference should be had to the accompanying drawings and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a front view schematically showing an embodiment of a chokemechanism constructed in accordance with the presentinvention;

FIG. 2 is a diagramfillustpating the principles of operation of thestructure, of the't kuigention; and

FIG. 3 is a graph'showing the relationship between the throttle openingand the choke opening in a carburetor constructed in accordance with theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1of the drawing, there is shown a carburetor 1 having a choke valve 2arranged on the upstream side thereof. The choke valve 2 may be turnedfrom its open position 2a, shown in brokenline form, to its closedposition 2b, shown in dot-dashline form. A throttle valve 3 is arrangedon the downstream side of the carburetor 1, with the closed position 3aof the throttle valve 3 being shown in broken-line form. Like the chokevalve 2, the throttle valve 3 may be turned from its closed position 3atoward an open position 3c by movement thereof in the direction of anarrow 3b.

The choke valve 2 is connected for rotationwith a valve shaft 4 whichdefines a fixed pivot axis for the choke valve 2. A lever 6 fixedlyconnected to the valve shaft 4 has attached thereto a choke wire 5 whichmay be pulled to rotate the lever 6 and the choke valve 2 in thedirection of the arrow 2c thereby moving choke I valve 2 toward itsclosed position.

The throttle valve 3 is arranged to rotate with a valve shaft 7 which isfixedly connected to an arm 8. The arm 8 is cooperatively associatedwith a lever 9 pivotally mounted on the shaft 7 through an intermediaryadjustment screw 10 which is used for adjusting the opening of the valveat the time of engine idling wliile the engine is in a cooled condition.Y

A connecting rod 13 is provided between the lever 6 and the lever 9 withone end of the connecting rod 13 being attached in an aperture 11 of thelever 6 to be freely rotatable therein. The opposite end of theconnecting rod 13 is similarly attached in an aperture 12 of the lever 9and is likewise rotatable relative thereto.

With the arrangement shown, the throttle valve 3 may be operated to beeither interdependently linked with the choke valve 2 or to be movableindependently thereof. The closing movement of the choke valve 2 in thedirection of the arrow 2c causes the opening movement of the throttlevalve 3 in the direction of the arrow 3b, as described above. Theopening movement of the throttle valve 3 upon actuation of anaccelerator pedal against the force of a return spring, however does notcause the closing movement of the choke valve 2, because the arm 8 fixedon the shaft 7 is turned away from the lever 9.

Referring now to FIG. 2, the points B and B represent positions of theaperture 11 at which a first joint between the lever 6 and theconnecting rod 13 is established. The positions C and C represent thepositions of the aperture 12 at which a second joint is establishedbetween the connecting rod 13 and the lever 9. when the choke is fullyopened, the aperture 1 l occupies position B. When the choke is fullyclosed, aperture 11 will be in position B. It will be seen that theaperture 11 may therefore lie on either side of a pair of lines labeledAC and AC during operation of the device. The line AC extends between aposition A, which represents the fixed pivot axis of the choke valve 2defined by the valve shaft 4, and the point C which represents theposition occupied by the aperture 12 when the throttle valve is arrangedto define an opening corresponding to the hot engine idling condition.The line AC connects the position A of the fixed pivot with a position Cwhich is occupied by the aperture 12 when the throttle valve is at anopening corresponding to cold engine idling.

Let it be assumed that choke valve 2 and the throttle valve 3 aresituated such that the former is fully open and the latter is closed soas to enable a hot engine to idle properly at normal temperature. Thiscondition is shown in full line in FIG. 1. Under this condition, if thechoke wire 5 is pulled to produce a choking effect, the lever 6 will bepivoted so that the choke valve 2 will be turned toward its closedposition. At the same time, the lever 9, the adjustment screw 10, thearm 8 and the throttle valve 3 will all be turned toward a positiontending to open the throttle valve 3 through operation of theinterconnecting linkage means embodied in the connecting rod 13. Thegeometrical relationships between the various components of the deviceare depicted in FIG. 2. It will be seen that with the choke valve 2 inits fully opened position, the included angle between the line AB andthe line BC will be smallest. As the lever 6 is swung toward thedirection of closing the choke valve 2, this angle will be increased toa maximum of 180 at which time the point B will lie along the lineextending between the fixed pivot axis represented by position A and theposition of the aperture 12 represented by the position C or C. As thepoint B swings past this line to the position B, the angle referred toabove will become an external angle greater than 180.

In the beginning of the pivotal movement of the lever 6 where theopening of the choke valve 2 is still large, i.e. where the choke valveis near its open condition, pivotal movement of the lever 9 will begreat so that throttle valve 3 will be moved toward the open conditionat a high rate. However, in the region where the opening of the chokevalve 2 is rather small, i.e. when the choke valve is near its closedpositon, the pivotal movement of the lever 9 becomes small so that thethrottle valve 3 is turned at a low rate.

The relationship between throttle valve opening and choke valve openingis varied in a manner represented by the solid line of the graph of FIG.3. When the choke wire 5 is pulled to its full extent so that the chokevalve is fully closed, the throttle valve 3 will occupy the position 30shown in dot-dash form in FIG. 1. In this position it is slightly openedto suit operation of a cold engine idling at a low temperature.

With reference to FIG. 3 it will be seen that, where a device such asthat of the present invention is utilized, the relationship betweenthrottle valve opening and choke valve opening will be in accordancewith the solid line appearing in the graph of FIG. 3. The dotted lineshown in FIG. 3 depicts the relationship which exists when conventionalcarburetor mechanisms are used and it will be seen therefrom that thethrottle valve opening changes in a proportional relationship relativeto choke valve opening. As a result, in the case of a conventionalcarburetor arrangement, the choke valve will be almost closed, forexample as indicated at the point 0 when the throttle valve is at anopening suited for cold engine idling at normal temperature. However, inthe case of the carburetor embodying the control mechanism of thepresent invention, the choke valve will be in a substantially openedcondition, as indicated by the point 0 shown in FIG. 3, when the throttle valve is at the same position as would produce an opening 9, in aconventional carburetor.

Accordingly, it will be seen that a carburetor embodying the controlmechanism of the present invention and functioning as indicated abovewill provide advantageous features in an engine exhibiting good warmupperformance and will greatly reduce the amounts of detrimentalcomponents contained in the exhaust gases.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

l. A control mechanism for a carburetor including a choke valve and athrottle valve each operable to be moved between a closed position andan open position, said control mechanism comprising linkage meansconnecting said throttle valve with said choke valve to render saidthrottle valve movable toward its open position in dependence uponmovement of said choke valve only when said choke valve moves toward itsclosed position, said linkage means including means for causing saidthrottle valve to be moved toward its open position at a relativelylower rate when said choke valve is moved toward its closed positionwithin a region near its closed position and means for causing saidthrottle valve to be moved toward its open position at a relativelyhigher rate when said choke valve is moved toward its closed positionwithin a region near its open position.

2. A control mechanism according to claim 1 wherein said choke valve ismounted to rotate about a fixed axis and wherein said linkage mechanismincludes a first lever connected to move with said choke valve aboutsaid fixed axis, a second lever detachably coupled through a third leverto move with said throttle valve, and a connecting rod extending betweensaid first and second levers, said connecting rod having one endpivotally mounted to said first lever at a first joint and a second endpivotably mounted to said second lever at a second joint, said linkagemeans being configured such that said first joint may be pivotally movedto be located on both sides of a line extending between said pivot axisand said second joint.

3. A control mechanism according to claim 2 wherein said linkagemechanism is configured such that during operation of said controlmechanism said first joint may be at a position which lies upon saidline extending between said pivot axis and said second joint.

4. A control mechanism according to claim 1 wherein as said choke valvemoves through a predetermined portion of its movement from its openposition to its closed position, said linkage mechanism causes saidthrottle valve to move in the direction of opening at a continuouslydecreasing rate of movement.

5. A control mechanism according to claim 1 wherein said linkagemechanism comprises first linkage means affixed with said choke valve tobe movable therewith, second linkage means affixed with said throttlevalve to be movable therewith, and abutment means located to enable saidfirst and second linkage means to move towards and into abutment witheach other when said choke valve moves toward its closed position andaway from abutment with each other when said choke valve moves towardsits open position, said first linkage means, said second linkage meansand said abutment means being interdependently configured to cause saidthrottle valve to be driven toward its open position by movement of saidchoke valve toward its closed position only when said first and secondlinkage means are in abutment with each other.

6. A control mechanism according to claim 5 wherein saaid abutment meansare adjustable to vary the point of abutment between said first andsecond linikage means.

7. A control mechanism according to claim 6 wherein said abutment meanscomprise screw means threadedly engaged with one of said first andsecond linkage means and extending therefrom for abutment with the otherof said first and second linkage means.

8. A control mechanism according to claim 5: wherein said throttle valveis fixedly mounted to a rotatable throttle shaft, and said choke valveis fixedly mounted to a rotatable choke shaft; wherein said firstlinkage means comprise a first choke-connected lever fixed to said chokeshaft, a third choke-connected lever freely rotatably mounted upon saidthrottle shaft, and a second choke-connected lever pivotally connectedto both said first and said third levers and extending therebetween;wherein said second linkage means comprise a throttle-connected leverfixedly mounted to said throttle shaft; and wherein said abutment meanscom-- prise means for effecting abutting engagement between said thirdchoke-connected lever and said throttleconnected lever.

1. A CONTROL MECHANISM FOR A CARBURETOR INCLUDING A CHOKE VALVE AND ATHROTTLE VALVE EACH OPERABLE TO BE MOVED BETWEEN A CLOSED POSITION ANDAN OPEN POSITION, SAID CONTROL MECHANISM COMPRISING LINKAGE MEANSCONNECTING SAID THROTTLE VALVE WITH SAID CHOKE VALVE TO RENDER SAIDTHROTTLE VALVE MOVABLE TOWARD ITS OPEN POSITION IN DEPENDENCE UPONMOVEMENT OF SAID CHOKE VALVE ONLY WHEN SAID CHOKE VALVE MOVES TOWARD ITSCLOSED POSITION, SAID LINKAGE MEANS INCLUDING MEANS FOR CAUSING SAIDTHROTTLE VALVE TO BE MOVED TOWARD ITS OPEN POSITION AT A RELATIVELYLOWER RATE WHEN SAID CHOKE VALVE IS MOVED TOWARD
 2. A control mechanismaccording to claim 1 wherein said choke valve is mounted to rotate abouta fixed axis and wherein said linkage mechanism includes a first leverconnected to move with said choke valve about said fixed axis, a secondlever detachably coupled through a third lever to move with saidthrottle valve, and a connecting rod extending between said first andsecond levers, said connecting rod having one end pivotally mounted tosaid first lever at a first joint and a second end pivotably mounted tosaid second lever at a second joint, said linkage means being configuredsuch that said first joint may be pivotally moved to be located on bothsides of a line extending between said pivot axis and said second joint.3. A control mechanism according to claim 2 wherein said linkagemechanism is configured such that during operation of said controlmechanism said first joint may be at a position which lies upon saidline extending between said pivot axis and said second joint.
 4. Acontrol mechanism according to claim 1 wherein as said choke valve movesthrough a predetermined portion of its movement from its open positionto its closed position, said linkage mechanism causes said throttlevalve to move in the direction of opening at a continuously decreasingrate of movement.
 5. A control mechanism according to claim 1 whereinsaid linkage mechanism comprises first linkage means affixed with saidchoke valve to be movable therewith, second linkage means affixed withsaid throttle valve to be movable therewith, and abutment means locatedto enable said first and second linkage means to move towards and intoabutment with each other when said choke valve moves toward its closedposition and away from abutment with each other when said choke valvemoves towards its open position, said first linkage means, said secondlinkage means and said abutment means being interdependently configuredto cause said throttle valve to be driven toward its open position bymovement of said choke valve toward its closed position only when saidfirst and second linkAge means are in abutment with each other.
 6. Acontrol mechanism according to claim 5 wherein saaid abutment means areadjustable to vary the point of abutment between said first and secondlinikage means.
 7. A control mechanism according to claim 6 wherein saidabutment means comprise screw means threadedly engaged with one of saidfirst and second linkage means and extending therefrom for abutment withthe other of said first and second linkage means.
 8. A control mechanismaccording to claim 5: wherein said throttle valve is fixedly mounted toa rotatable throttle shaft, and said choke valve is fixedly mounted to arotatable choke shaft; wherein said first linkage means comprise a firstchoke-connected lever fixed to said choke shaft, a third choke-connectedlever freely rotatably mounted upon said throttle shaft, and a secondchoke-connected lever pivotally connected to both said first and saidthird levers and extending therebetween; wherein said second linkagemeans comprise a throttle-connected lever fixedly mounted to saidthrottle shaft; and wherein said abutment means comprise means foreffecting abutting engagement between said third choke-connected leverand said throttle-connected lever.